1. Field of the Invention
This invention relates to a toolholder with selectable critical angles, such as a lead angle, a trailing angle, a rake angle, and a flank clearance angle. More particularly, this invention relates to machine tool for turning and threading operations, such as a lathe or a machining center, that allows a specified relationship between the insert geometry and the workpiece to be selectively determined by a software program of a numerically controlled machine tool to maintain a critical angle between the insert and the workpiece as the geometry of the workpiece changes.
2. Description of the Related Art
In most advanced machine tools, movement and control of the machine and its components are actuated by computer numerical controls (CNC). These machine tools are usually equipped with one or more turrets. Each turret can be equipped with a variety of tools and performs several operations on different surfaces of the workpiece.
Typically, a turning operation is performed in two linear axes, such as the X- and Z-axes. A third linear axis, such as the Y-axis, can be added to a turning machine tool to support milling operations in that axis, but not turning operations. As a result, a dedicated toolholder has been required for each desired unique lead angle, thereby increasing the costs associated with the machining operation.
In addition, the rake face of the cutting insert in conventional threading tools is in the X- and Z-axes. As pitch angles increase, the angle between the rake face and the thread becomes significant. Likewise, the clearance angles must be changed, in particular on the leading edge where the angle of the thread may exceed the typical clearance angles, resulting in interference. Therefore, cutting inserts are frequently ground specifically for threads of a specific pitch angle. Manufacturers of such products with various pitch angles must therefore purchase and inventory cutting inserts specifically for each pitch angle.